The present invention relates to a method and apparatus for automatically identifying a bottle which is transparent to a laser beam according to the mold in which it was made. More specifically, the invention relates to a method and apparatus for automatically identifying and ejecting defectively formed bottles.
It is well-known in the art to automatically identify a container, regardless of transparency, by a variety of surface markings placed on the exterior of the container. Depending upon the purpose for which an apparatus has been designed, these surface markings can indicate any of a number of events. For example, U.S. Pat. No. 2,647,799 discloses a machine which sorts a procession of metal cans according to the contents of the cans. The contents are denoted by the application of non-reflective stripes on the exterior of the can. More specifically, the precise location of a non-reflective stripe connotes the nature of the contents of the can.
In the sorting machine of said patent, a light source and detector pair scans a limited area of the can exterior. All possible locations for a stripe are scanned by a series of such source-detector pairs. Accordingly, a multiplicity of light sources and detectors is required in order to scan all possible stripe locations. The machine, then, requires a multiplicity of inspection stations to identify each container. The identification of a container by such a machine is unduly time-consuming and does not lend itself for use with transparent bottles since the exterior of such a bottle is non-reflective.
Techniques and devices for automatically identifying a transparent bottle are also known in the art. One such technique is to mark the exterior of the bottle according to the mold in which that bottle was formed and to mechanically count the number of marks appearing on the bottle. For example, in U.S. Pat. No. 3,301,396 for "Method of and Apparatus for Classifying Glass Bottles" there is described a machine for automatically identifying the source of a glass bottle according to the number of surface markings appearing on the bottle exterior. In particular, a number of projections is formed on the bottom of the bottle. Bottles having different numbers of projections are formed in respectively different molds. The mere number of projections, therefore, identifies the source of the bottle. A processing of the bottles is fed through a plurality of inspection stations, each of which contains a set of mechanically operated scanning switches which control an ejection channel. Upon reaching the inspection station, the bottle -- and therefore the entire procession -- is stopped and the scanning switches are brought into physical contact with the bottom of the bottle. With the bottle stationary, the switches rotatably contact the projections on the bottom of the bottle. The switches, then, provide a count of the total number of projections. Since the number of projections corresponds to a particular mold, the count serves to identify the source of the bottle. In the course of computing the number of projections, the spatial distribution of the projections is immaterial; the switches respond identically to all bottles having the same number of projections regardless of the location and spacing thereof.
A chief disadvantage of the device described in U.S. Pat. No. 3,301,396 is the necessity for stopping each bottle at the inspection station. That is, a considerable amount of time is wasted by interrupting the procession to permit the inspection of each bottle. A further disadvantage of the apparatus is that the number of projections which can appear on the bottle exterior is limited by the available surface area and the size of the projections. Accordingly, there is a practical limit to the number of projections which can be counted. As a result, the machine described in said patent can be used to identify a bottle with a limited number of molds. A plant using large numbers of molds, then, will require several of these machines. Furthermore, since the projections must extend considerably beyond the surface of the bottom of the bottle to contact the scanning switches, the projections themselves may introduce defects in the bottle due to strain in the glass surface skin; and a projection may fail to operate a switch due to bulge or sag in the bottom of the bottle, causing an erroneous count and a mistaken identification.
A principal advantage of the present invention is that the bottles are inspected for identification with a preselected mold without interrupting the flow of the main procession toward the packing station.
Another advantage of the invention is that only one inspection station is required to identify each bottle in the procession and a single laser and sensor pair is used to inspect the entire procession.
An additional advantage is that a single machine can be used to identify a bottle with a large number of molds.
Further advantages appear hereinafter.